The present invention relates to enzyme-containing compositions and methods employing such enzyme-containing compositions for contact lens cleaning. More particularly, the invention relates to such enzyme-containing compositions and to contact lens cleaning methods employing enzyme-containing compositions which provide for deactivating the enzyme after the contact lens has been effectively enzymatically cleaned.
The growth of the contact lens industry has led to a dramatic increase in the number of contact lens care systems. One goal of the lens care industry has been to simplify lens care systems while, at the same time, providing for effective, high quality care, and safe and comfortable wearing of the treated contact lenses.
In the normal course of wearing contact lenses, debris, such as tear film and proteinaceous, oily, sebaceous and related organic matter, has a tendency to deposit and build up on the lens surface. As part of the routine care of a contact lens, it should be cleaned to remove this debris. If this debris is not removed, the lens can become uncomfortable to wear and may even damage the eye.
One approach to removing debris buildup from contact lenses has been to subject the debris laden lenses to enzymatic action. For example, Karageozian U.S. Pat. No. 3,910,296 discloses the use of proteases for cleaning contact lenses.
Ogata U.S. Pat. No. 4,285,738 discloses the use of compositions comprising urea and/or an acid salt of guanidine, a reducing agent and a proteolytic enzyme, with or without additionally heating, to clean contact lenses. Proteolytic enzymes disclosed include papain, trypsin, alpha-chymotrypsin, pronase p from S griseus and proteinase from B. subtilis.
Anderson U.S. Pat. No. 4,521,254 discloses methods and compositions for cleaning contact lenses comprising an endopeptidase such as bromelain and a carboxy peptidase enzyme.
Schaefer U.S. Pat. No. 4,609,493 discloses contact lens cleaning compositions containing a proteolytic enzyme, an anionic surfactant, a calcium chelating agent and urea. The calcium chelating agent is disclosed as a principal lens cleaning ingredient which does not significantly decrease the activity of the enzyme. Preferred enzymes are pancreatin and papain.
Ogunbiyi U.S. Pat. No. 4,614,549 discloses methods for cleaning and thermally disinfecting contact lenses and deactivating the enzymes used for this process through the use of proteolytic enzymes in aqueous solutions which are heated to an elevated temperature between 60.degree. C. and 100.degree. C.
Ogunbiyi U.S. Pat. No. 4,614,549 discloses the use of activator-free microbial-derived proteolytic enzymes as well as chelating agents such as salts of ethylene diamine tetraacetate (EDTA) to bind metal ions in solution such as calcium, which might otherwise react with lens protein and collect on lens surfaces.
Ogunbiyi U.S. Pat. No. 4,690,773 discloses methods for cleaning contact lenses with an activator-free enzyme solution comprising an aqueous solution containing a protease derived from a Bacillus, Streptomyces or Aspergillus microorganism. The microbial proteases disclosed require no additional activators or stabilizers and are not inhibited when in the presence of a chelating agent. This patent discloses that enzymes which are inhibited by chelating agents are generally unsatisfactory for use with contact lenses. Also, this patent discloses that proteases should be active at a pH range of from 5 to 8.5.
Huth et al U.S. Patent Reissue 32,672 discloses methods for simultaneous cleaning and disinfecting of contact lenses using a disinfecting amount of peroxide and peroxide-active enzymes. Neutral, acidic or alkaline enzymes, as well as metallo-proteases, may be used.
Mowrey-McKee U.S. Pat. No. 5,096,607 discloses methods for simultaneously cleaning and disinfecting contact lenses using polymeric quaternary ammonium salts or biguanides, a proteolytic enzyme and an aqueous system wherein the osmotic value is adjusted to a level which does not substantially inhibit the activity of the antimicrobial agent. This patent discloses that additional components, such as chelating and/or sequestering agents, may be added to or incorporated into the enzyme which do not substantially decrease the activity of the enzyme.
None of the aforementioned patents discloses methods or compositions to inactivate cleaning enzymes via ionic regulators in the absence of heat input.
An important concern relating to the enzymatic cleaning systems currently being employed is the need to remove the enzyme from the lens prior to placing the cleaned lens in the eye. Placing a lens contaminated with cleaning enzyme into the eye may be potentially detrimental to the eye. This potential problem, if any, is avoided currently by rinsing the contact lens free of cleaning enzyme prior to placing the cleaned lens in the eye. However, this rinsing step may adversely impact user compliance since the user may consider such rinsing unnecessary and, as a result, place active enzyme in the eye. Additionally, in some instances, rinsing the contact lens free of cleaning enzyme may be insufficient to eliminate discomfort, irritation and detrimental ocular effects due to lens-bound active enzyme which may desorb or elute from the contact lens into the eye.
An additional concern relating to the enzymatic cleaning systems currently employed is that the lenses are often rubbed between the thumb and forefinger or in the palm of the hand, to remove the loosely adherent debris still remaining on the contact lens. Rubbing lenses often causes tearing and thus loss of the lens. The amount of debris remaining on the lenses is related to the cleaning efficiency of the enzyme composition which, in turn, is related to the concentration of enzyme employed. Current enzyme compositions must utilize lower concentrations of enzyme to avoid possible ocular surface damage if they are placed into the eyes. It would be advantageous to provide a system in which the lens is effectively cleaned without such rubbing.